Physiological and anatomical responses to drought stress differ between two larch species and their hybrid

Abstract

Key Message Hybrid saplings were more reactive to soil water deficit than Japanese and European larch. European larch had hydraulically safer wood and anisohydric behavior, Japanese and hybrid larch showed isohydric strategy. Abstract Deciduous larch species could be an alternative to evergreen conifers in reforestation, but little is known about drought sensitivity of their saplings. The effect of an experimental drought on hydraulics and quantitative wood anatomy was tested on saplings of European larch (EL, Larix decidua), Japanese larch (JL, Larix kaempferi) and their hybrid (HL). Across species, biomass, transpiration rate and relative water content were higher in controls than in drought stressed trees, but transpiration efficiency was lower. JL had the highest transpiration efficiency under drought, and EL the lowest, coinciding with slower growth of EL. Wood of EL formed before drought was hydraulically safer as shown by higher wall/lumen ratio and lower pit cavity area. EL neither had a significant increase in transpiration efficiency nor a reduction in transpiration rate under drought, suggesting that the stomata remained open under soil water deficit. HL saplings were the most reactive to water shortage, indicated by intra-annual density fluctuations and a decrease in relative water content of the sapwood. Significant reduction in transpiration by HL suggested a higher stomatal sensitivity, while the same leaf surface area was maintained and radial growth was still similar to its best parent, the JL. The latter showed a significantly lower leaf surface area under drought than controls. EL, with its hydraulically safer wood, followed an anisohydric behavior, while JL and HL revealed an isohydric strategy. Altogether, our results suggest species dependent acclimations to drought stress, whereby HL followed the strategy of JL rather than that of EL.

Contact Mechanics between Torus and Pit Border for Developing Air-Seeding Seal in Aspirated Bordered Pits

“…There has been a growing interest in the influence of the bordering pit on conifer hydraulic safety [6][7][8]. The literature extensively documents the observation of contact between the torus and the pit border in aspirated pits as a means to avoid air-seeding leakage between tracheids [9][10][11]. This phenomenon (Figure 1) was also found in a greenhouse experiment conducted at Northeast Forest University in Harbin, China, specifically investigating water stress conditions.…”

Modeling of the Statistical Distribution of Tracheids in Conifer Rings: Finding Universal Criterion for Earlywood–Latewood Distinction

“…There are significant differences between species in the shapes of scatter plots and in the location/density of earlywood and latewood clusters, reflecting the specific features of the anatomical structure. This variability reflects species-specific features with regards not only to tree size (height), but also to ecophysiological traits and species-specific adaptations to habitat conditions [46][47][48][49]. Taking into account the estimates of the threshold value k = 0.105-0.136 obtained in this work, we can conclude that the usage of one universal rigid threshold of k, as both interpretations of the Mork criterion suggest, quite often does not reflect the actual intra-seasonal variability of the anatomical structure in conifer wood.…”

Ready for Screening: Fast Assessable Hydraulic and Anatomical Proxies for Vulnerability to Cavitation of Young Conifer Sapwood

“…Microphotography was achieved with a Leica DM4000 M microscope equipped with a Leica DFC320 R2 digital camera and Leica IM 500 Image Manager image analyzing software (Leica, Wetzlar, Germany). Cell wall thickness and tracheid dimensions were measured by means of Image J software [39] in the first ten radial earlywood cell files [28] of the latest annual ring in four different locations around the stem. Lumen diameters (b) and double cell wall thickness (t) in the radial (b r , t r ) and tangential (b t , t t ) directions of 20 tracheids (Figure 1a,b) were measured.…”

“…Anatomical proxies for P 50 offer the advantage that samples do not need to be fresh and that hydraulic vulnerability can be determined retrospectively for selected annual rings. The approach of relating drought response of trees to "constitutive wood anatomy" is based on works by [27,28] who found that the wood formed (often several years) before drought stress impacts the sensitivity to drought in sapwood of Picea abies and different Larix species. Drought induced dieback [27] or growth decreases [28] are more strongly related to (t/b) 2 measured in the tangential rather than in the radial direction.…”

“…The approach of relating drought response of trees to "constitutive wood anatomy" is based on works by [27,28] who found that the wood formed (often several years) before drought stress impacts the sensitivity to drought in sapwood of Picea abies and different Larix species. Drought induced dieback [27] or growth decreases [28] are more strongly related to (t/b) 2 measured in the tangential rather than in the radial direction. Wood density is a very good proxy for hydraulic vulnerability in conifers [20,29] and is easy to measure; however, when the intention is a retrospective analysis at the annual ring level, techniques such as X-ray or high-frequency densitometry need to be applied [30,31].…”